The present application claims priority from Japanese Patent Application No. 2015-109263 filed on May 29, 2015, the content of which is hereby incorporated by reference into this application.
In recent years, a touch detection device which is so called touch panel capable of detecting an externally-approaching object has attracted attention. A touch panel is mounted on a display apparatus such as a liquid crystal display apparatus or integrated with a liquid crystal display apparatus so as to be provided as a display apparatus with a touch detection function.
As the externally-approaching object, a touch panel enabled to use, for example, a pen is known. By enabling the touch panel to use a pen, for example, a small area can be assigned or hand-written characters can be input. Various techniques to detect the touch by a pen are known. As one of the various techniques, an electromagnetic induction system is known. In the electromagnetic induction system, high accuracy and high handwriting pressure detection accuracy can be achieved, and a hovering detection function in a state in which an externally-approaching object is separated from the touch panel surface can be also achieved, and therefore, the system is a leading technique as the technique to detect the touch by a pen. The touch detection technique using the electromagnetic induction system is described in, for example, Japanese Patent Application Laid-Open Publication No. H10-49301 (Patent Document 1), Japanese Patent Application Laid-Open Publication No. 2005-352572 (Patent Document 2), and Japanese Patent Application Laid-Open Publication No. 2006-163745 (Patent Document 3).